The conventional method of orthodontic tooth movement, as practiced in the prior art, has been one of constant pressure applied to the tooth in order to move it through the adjacent bone. Constant pressure applied to the periodontal membrane by traditional orthodontic appliances causes the periodontal fibers to become cell free which results in standstill of the tooth. Compression of tissue results in reduced blood supply and tissue necrosis, and the tooth will not move again until the bone subjacent to the hyalinized tissue has been eliminated by undermining resorption. Generally, it is essentially the magnitude of the force which will determine the duration of the hyalinization. Moreover, the strong forces produce a wide hyalinization area of long duration. A discussion of this phenomenon may be found on Pages 76 and 97 of Current Orthodontic Concepts and Techniques, T. M. Graber, Editor, published by W. B. Saunders & Co. 1969.
When a tooth is tipped by a continuous force exerted on it by a usual prior art orthodontic appliance, the periodontal membrane is compressed in a circumscribed area situated close to the alveolar crest. This area becomes cell free and the blood vessels are occluded, and osteoclastic activity is reduced to a minimum. A description of this occurrence may be found, for example, at Page 497 of Orthodontic Principles and Practice by Graber, 2d Edition, published by Saunders & Co., 1967. If the pressurized area of periodontal membrane during the movement of a tooth by an orthodontic device is not compressed by strong forces, then the formation of osteoclasts, the cells responsible for resorption of bone, will be enhanced. The flow of blood to the area will not be restricted, and consequently osteoclastic activity will become more vigorous and bone resorption will be increased.
U.S. Pat. No. 4,229,165, which issued to the present inventor, discloses an orthodontic appliance which introduces pressure impulses to the tooth being treated, rather than a continuous force. With every pressure impulse from the appliance, the tissue pressure in the periodontal membrane and adjacent bone tissue is increased. When pressure is relaxed, the tissue fluid in the periodontal membrane and adjacent bone tissue is reduced. This fluctuation from high pressure to low pressure in the periodontal and adjacent tissue results in a pump-like action that sucks blood and tissue fluid into the area, and which then expels fluid from the area, for each cycle of operation. This serves to increase cellular action around the moving tooth, giving rise to more osteoclasts for bone resorption and more osteoblasts for bone aposition.
The active exchange of fluid during the pulsating operation of the appliance described in the patent helps to carry the by-products of bone resorption out of the resorption area. The pulsating tooth movement applied by the appliance is psychological and dynamic in nature, rather than pathological. Because the pulsation pressure exerted by the appliance does not result in areas of hyalinization and necrosis thereis no root resorption or horizontal bone lotion. The pump-like action of the tooth being pulsated by the appliance described in the patent is the same on the tension side of the tooth as on the compression side, but opposite in the timing cycle. On the tension side of the tooth, the increased blood supply results in increased cellular activity.
As a result, the use of the pulsating orthodontic appliance of the patent results in faster movement of the tooth, reduction of root resorption during orthodontic movement, reduction of horizontal bone loss during bone reconstruction, reduced discomfort from heavy orthodontic pressures, and reduction in tooth extrusion from their bony sockets when pressurized. The total effect resulting from the use of the orthodontic appliance of the patent is that tooth movementis of a psychological nature causing little or no irreversible results to the tooth or horizontal level, and expediting the travel of the tooth along its path through the adjacent bone so as to obtain the most rapid orthodontic movement in a painless environment.
The appliance of the present invention uses an extra oral headgear to achieve the pulsation effect, and it is even more effective than the appliance described in the patent. The source of the pulsations in the appliance of the invention is in the natural masticating action of the patient's lower jaw, and the pressure pulse delivered by the headgear occurs when there is no occlusal pressure on the teeth and is, therefore, more effective. This is because, at that moment there is no occlusion that would impede distalization of the molars being treated. Moreover, the pressure pulse from the occlusal pad is directed in a manner to prevent the headgear from causing extensions of the maxillary molars.
As described briefly above, in the practice of the present invention, a resilient elastic pad is mounted on the occlusal surface of one of the maxillary molars, and each time the lower molars close on the upper molars this pad is squeezed, and liquid in the pad is translated under pressure into a resilient elastic reservoir which is attached to the headgear. The appliance may be unilateral in operation, or bilateral, depending upon the particular needs of the patient.
The pressure that builds up in the anterior reservoir presses back on the molars being treated when the lower molar releases the pressure of the occlusal pad. This provides an intermittent pulsation of the pressure delivered by the headgear. As noted above, the source of the pulsation is in the natural masticating action of the lower jaw, and the pulsation pressure that is delivered to the molars being treated occurs when there is no occlusal pressure on the molars and consequently is most effective, since it occurs at the moment when there is no resistance from the occlusion that would otherwise impede movement of the molars. The vertical pressure from the occlusal pad also prevents the headgear from causing extension of the molars being treated.
Every time a person swallows, his teeth come together to result in the pulsating pressure. since a preson swallows over five thousand times daily, adequate pulsation frequently is provided.